Undercarriage or landing gear for aircraft



Sept.'4, 1928. 1,682,894

J. DE LA,C|ERVA UNDERCARRIAGE OR LANDING GEAR FOR AIRCRA FT Filed March26, 1927 /)v VEN 7701?.

J. DE LA C/ERVA ,12

nr-rrs.

enema Sept. 4, 1923.

UNITED STATES PATENT oF ICE.

uunnncannrnon on LANDING em non Application fled March 28,1927, SerialNo. 178,708, and in Great Britain April 7, 1826.

This invention relates to motor-carriages or landing ear for aircraft ofthe type embodying a reely rotative hinged-wing system such as thatdescribed in my patent specification No. 1,590,497.

In order to prevent dama e to the art1culated wing structure by sud enstrong gusts of wind it is therefore desirable that the angle ofincidence of the'wings in a machine of this character should heasnearly. as possible zero when the aircraft is stationary on the ground.It is of course necessary on the other hand essential that thewingsshould have a relatively great positive incidence when taking off, andmy present inventlon aims at providing an under-carriage for aircraft ofthis character such that the air-craft has two positions of rest, theone in which the incidence of the lifting surfaces 1s ap proximatelyzero to enable the machine 1105 stand with little or no danger, and theother" in which the incidence is sufficiently positive to enable themachine to take oil.

Primarily, according to the present 111ve ntion, I provide anunder-carriage, for aircraft of the character referred to, in which thelanding elements proper, such as wheels or wheels and skids are sodisposed with relation to the centre ofgravity of the aircraft that thelatter when at rest possesses two positions of uilibrium, one 1n wl11chthe longitudinal axis of the aircraft is suhstantially horizontal andthe angle of 11101-- dence, of the wings approximately zero, and theother in which the tail-skid or other rearm'ost lan element is incontact with the ground or oter surface andthe angle of incidence of thewings is positive.

For thispurpose the under-carnagemay embody a pair or more of pr ncipallanding wheels so disposed that thenaxles he in rear of the verticalplane through the centre of gravity of the aircraft when the latter isrestin with its longitudinal axis substantially orizontal, and inadvance of said ver- "tical plane when the tail-skid or other rearmostlanding elementis in contact with the ground, and a wheel or wheels inadvance of the principal wheel or wheels to support the aircraft in thefirst mentioned stationary position of equilibrium.

To enable the aircraft to'hereadilylmoved 7 from one sition ofuilibriuni to the other the lacement o the axles of the principal laznwheels from the vertical plane through the centre of gravity of the thepilot by raising or lowering the elevator or controllable tail plane,may cause the slip stream from the propeller or propellers to rock theaircraft from one of the said positions to the other.

To support the aircraft in its substantially horizontal position of zeroincidence either forwardly disposed landing wheels or skids may be emploed. In an amphibian aircraft the principal wheels and the forward wheelsor skids may be mounted in or upon the floats in the case of. seaplanesor the hull in the case of flying boats, and since the forward landingspeed is small it may be unnecessary to provide means for withdrawingthe wheels or skids into the floats or for landing upon water.

A further feature of the present invention consists in mounting theskids, or floats in the case of seaplanes, in such a manner that theyare permitted a restricted pivotal movement about vertical axes, withsuitable centralizing springs or other devices acting to maintain saidskids or floats normally parallel to the fuselage but allowing them,

the hull,

aircraft may be relatively small so that 4 when the aircraft lands witha lateral speed,

to set themselves in the direction of the resultant speed. To accomplishthis the vertical axes of rotation of the skids or floats shouldobviously he in advance of the'centre of friction with the surfacelanded upon, in order to keep the landing elements steady duringsliding.

The present invention is diagrammatically I illustrated in theaccompanying drawings in which for the sake of clearness only the nearsidelanding elements are shown.

Fig. 1 is a side elevatlonal view of an aircraft of the type referred toillustrating the employment of forward landing wheels in conjunctionwith the principal wheels.

Fig. 2 is a similar view but showing the forward landing wheels replacedby skids.

- Fig. 3 shows an application of the inven-.

tion to a seaplane, and

Fig.7 '4 diagrammatically illustrates ararrangement in which the landingelements are capable of restricted pivotal movement about vertical axesas aforesaid.

i In all of these Figs...A denotes the fuse- V lage of the aircraft andB B the longitudinal axis, being the axis of thrust of the propellor C.The' int :1: represents the centre of gravity 0 the aircraft and Ddenotes one of a pair or more of principal landing wheels secured to thefuselage through any convenient s stem of shock absorbers, diagrammaticaly indicated at D.

The line G G represents the horizontal surface upon which the aircraftrestsin one position and G G the horizontal surface in the otherposition. The axles D of the wheelsD are so disposed with relation tothe centre of avity a; of the aircraft that thevertical p ane,represented by the line a: '0, through the centre of gravity :0 is inadvance of the axles D when the aircraft is in substantially horizontalposition, which is therefore a position of equilibrium. In this positionthe. angle of incidence of the wings E is substantially zero. Althoughonly forwardly .and rearwardly extending wings of the rotative systemare shown, it will be obvious that the Incidence of laterally extendingwings will be more nearly zero than when the aircraft is tilted back ashereafter mentioned.

In Fig. 1 a forwardly disposed wheel or wheels F is or are provided tomaintain the substantially horizontal position of the aircraft and inFig. 2 a skid or skids H are employed for this purpose, the skids beingused as aforesaid only in cases where the forward landing speed isrelatively very small.

The other position of equilibrium of the aircraft is that represented bythe contact of the principal wheels D and a tail skid J with the surfacerepresented by the line G G the aircraft having been rockedback aboutthe axles D In this osition the vertical plane represented by tile linea: 3 through the centre of gravity m is behind the axles D therebyensuring the state of equilibrium in this position, in which the angleof incidence 0 the wings E is sufficiently positive to. enable theaircraft to take off.

The displacement of the lines or and a: y from the wheel axles D ispreferably small, for instance such that the couple roduced by theaction of the slip stream rom the propellor C upon the lifted ordepressed elevator K is sufiicient to rock the aircraft from oneposition to the other.

In Fig. 3 the principal landing wheels D and skids H are mounted uponthe floats L of a seaplane; the condition as to the relative positionsof the axles D and the centre of gravity :1: of the aircraft being thesame as that above described.

' Fig. 4 illustrates diagrammatically a construction in which each skidH together with its landing wheel D is mounted to permit a restrictedpivotal movement about a vertical axis M which is in advance of thecentre of friction of the said landing elements with the surface landedupon. The landing elements are in this manner enabled to "set themselvesparallel to the line of the result ant speed whenever 'the aircraftlands with a lateral as well as a forward speed. Elastic elements (notshown) of any suitable t pe, e. springs, are provided to maintain tieski s normally parallel to the longitudinal axis of the aircraft or thedirection of flight.

.This construction may be similarly aplied to the form of constructionshown in ig. 1 where forward landing wheels are used.

What I claim is a '1. An aircraft comprising a fuselage and propellingmeans, a supporting system comprising freely rotative wings articulatedto the axis of rotation and adapted to be revolved by the relative airflow during flight and an undercarriage comprising principal landingwheels having thclr axles disposed close to a transverse vertical planepassing through the centre of gravity of the aircraft, advanced landingelements disposed in front of the principal landing wheels to supportthe aircraft in stationary equilibrium with its longitudinal axissubstantially horizontal and the angle of incidence of the wing systemapproximately zero, and-a rear land; ing element such as a tail-skid tosupportthe aircraft in con'unction with the principal landingwheelsinanother stationary position of equilibrium in which the wing system hasa relatively great positive angle of incidence.

2. An aircraft comprising a fuselage and propelling means, a supportingsystem com:

prising freely rotative win s articulated to the axis of rotation andadapted to be revolved by the relative airflow during flight and anundercarriage including principal landing wheels, supplementarysupporting means pivotall mounted in front of the principal lan ingwheels, said landing wheels being so disposed that their axles lie inthe rear of the vertical plane thiough the centre of gravity of theaircraft when resting on the wheels and supplemental supporting meansand the said wheels being in advance of said vertical plane when thetailskid of theaircraft is in contact with the ground.

JUAN on LA CIERVA.

